Hi jcable, and welcome to the community! 
Where is the salt stored currently if not in the DB? You need the salt to check the password hash. Your current application would have to know it to verify the hash. In order to import it into Auth0, you will need it as well.
According to this SO, the salts should be in the pass column: database - Getting password hashes and salts from Drupal 7 - Drupal Answers